Evaluate checkboxes with Javascript

<form>
january &nbsp; <input type="checkbox" name="month"> 
  <br><br>
february &nbsp; <input type="checkbox" name="month"> 
  <br><br>
march &nbsp; <input type="checkbox" name="month"> 
  <br><br>
...and so on

<input type="button" onclick="evaluate()" value="select">
</form>

<script type="text/javascript">
function evaluate(){ 
var limit=document.getElementsByName('month').length;
    for (i=0; i<=limit-1; i++){
        if (document.getElementsByName('month')[i].checked){
            ¿¿¿???
        }
    }
}
</script>

january &nbsp; <input type="checkbox" name="month" value="01">
february &nbsp; <input type="checkbox" name="month" value="02">

function evaluate(){ 
var a=document.getElementsByName('month').length;
var j=0;
var selected_mo= new Array();
    for (i=0; i<=a-1; i++){
        if (document.getElementsByName('month')[i].checked){
            selected_mo[j]= document.getElementsByName('month')[i].value;
            j++;
        }
    }
}